[Oeva-list] A123 charging (ZEVA study)

Jeff Kim jkim.shurepower at gmail.com
Sun Oct 14 01:01:59 PDT 2007


Has anyone heard about any independent testing of Enerdel's Lithium
Batteries?

www.enerdel.com

http://www.indystar.com/apps/pbcs.dll/article?AID=/20071009/BUSINESS/71009078


According to Enerdel, they have some pretty impressive advantages.

Jeff K.

On 10/13/07, Gary Graunke <gary at whitecape.org> wrote:
>
> I certainly enjoyed the ZEVA study, and appreciate a comparison of the
> LiFePO cells (which are wonderful). First of all, let me say that I have
> been driving 166V (and 166 lbs!) of A123 cells since July 3 (made by
> repackaging 23 DeWalt DC9360's into a 36X3X9 box, 5 boxes for now). I
> have a Agilent 34970a data acqusition system in the car (for now) to
> measure voltages from all 50 cell groups during driving and charging.
> (I'll try to get some of that data published--I'm way behind updating my
> website). They run so cool that I'm not even cooling them (not even in
> summer). However, I need to do a better job of measuring the temperature
> inside the cells (all channels are taken measuring voltage). Bottom
> line--I'm about 6X lighter than lead AGM batteries, partly due to the
> relatively high power of the A123's (less Peukert effect). I ordered an
> eval kit from A123, and found their data to be very accurate. I used a
> Sorenson DCS8-125 power supply, an ACDC EL750BR-2-1 electronic load in
> CC mode, and an Agilent 34970a data acquisition system. I used 4 gauge
> wire for the connections. So, back to the study. The discharge part
> seems ok--I'd have to run constant resistance mode to recreate it.
> Normally I use constant current, but a better measure of actual EV
> performance is constant power. But A123's at least are so flat that it
> doesn't make a lot of difference. The charging part probably needs a bit
> of work. Notice that the battery voltage does not reach 3.6V until after
> the power supply has gone into CV mode. This is especially apparent on
> the surprising 2C charging on the A123's. I suspect that there is a bit
> of resistance in the wiring between the power supply and the cell under
> test that is not terribly significant until you reach higher currents.
> Note that the A123 cells also have the highest capacity, and 2C is
> higher on them compared to the other cells. This can be remedied by
> using larger wire between the power supply and cell, and by using a
> Kelvin connection (a separate pair of wires to measure the voltage at
> the cell independent of the wires used to deliver the power). Some lab
> supplies will use Kelvin connections to regulate the voltage, and will
> thus deliver 3.6V at the cell rather than their output terminals. I
> usually don't bother to do this, but it does make a difference at the
> higher currents. The LiFePO4 cells are great, and it's good to see more
> vendors getting into them. It's also great to see real data (despite any
> shortcomings) from independent testers. Thanks for going to the trouble
> of testing and sharing the results! Gary ev.whitecape.org (hopefully
> I'll get going on updating it). ============================= Date: Sat,
> 13 Oct 2007 12:51:04 +0800 From: Ian Hooper <ian at zeva.com.au> Subject:
> Re: [EVDL] Price Winner - PHET PE-1150 To: Electric Vehicle Discussion
> List <ev at lists.sjsu.edu> Message-ID:
> <609D4478-FE66-4E52-8C51-8F25502295CB at zeva.com.au> Content-Type:
> text/plain; charset=US-ASCII; delsp=yes; format=flowed The page has been
> accessed almost 4000 times now - makes it all worthwhile :) My test rig
> was a little "grass roots" I admit :) but hopefully people will realise
> this and won't take the results for gospel. I like to think that at the
> very least testing a variety of cells on the same rig gives useful
> qualitative/comparative results. -Ian On 13/10/2007, at 12:53 AM, Travis
> Gintz wrote:
>
> > > I thought it was a good read anyway :)
> > >
> > > Some guy on another list (Doug Korthof, Electric vehicles for sale)
> > > thought the data was innacurate, and when I asked him to point out
> > > "WHY" he didn't respond. I'm still curious why he thought the data was
> > > full of error. I'm not saying its 100% dead nuts on, but its very
> > > close. I worked at GE testing tons of stuff (power supplies, IGBT's,
> > > controllers) and It looked like it was set up pretty well.
> > >
> > > On 10/12/07, Dan Frederiksen <danfrederiksen at gmail.com> wrote:
> >
> >> >> it was posted here a few days ago and Ian (zeva) is a member of this
> >> >> list : )
> >> >>
> >> >> Arak Leatham wrote:
> >> >>
> >>
> >>> >>> Here's a very interesting article putting 5 different LiFePo
> >>> >>> batteriesagainst eachother in charge and discharge tests. Good
> >>> >>> data, lots ofgraphs, cost effectiveness, cost per Ah, cost per
> >>> >>> cell..... etc. Goodread.
> >>> >>> http://zeva.com.au/tech/LiFePO4.php
> >>> >>> Found on Hackaday.com
> >>> >>> regards,Travis Gintz1986 Honda VFR AC conversionHttp://
> >>> >>> blog.evfr.net>>>
> >>> >>>
> >>> >>>
> >>>
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